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<html>
  <head>
    <meta charset='utf-8'>
    <meta name='viewport' content='width=device-width, initial-scale=1, user-scalable=no'>
    <meta name='mobile-web-app-capable' content='yes'>
    <meta name='apple-mobile-web-app-capable' content='yes'>
    <link rel='icon' type='image/png' sizes='32x32' href='favicon-32x32.png'>
    <link rel='icon' type='image/png' sizes='96x96' href='favicon-96x96.png'>
    <link rel='stylesheet' href='css/common.css'>

    <title>Inline Session</title>
  </head>
  <body>
    <header>
      <details open>
        <summary>Inline Session</summary>
        <p>
          This sample demonstrates use of an 'inline' XRSession to present
          content on the page prior to entering XR presentation with an
          immersive session. The viewer pose can be adjusted by clicking and
          dragging with mouse or touch.
          <a class="back" href="./">Back</a>
          <p>
            <input id='vertFOV' value='90' min='30' max='150' step='10' type='range'/><br/>
            <label id='vertFOVLabel' for="vertFOV">Vertical FOV: </label>
          </p>
        </p>
      </details>
    </header>
    <script type="module">
      import {WebXRButton} from './js/util/webxr-button.js';
      import {Scene} from './js/render/scenes/scene.js';
      import {Renderer, createWebGLContext} from './js/render/core/renderer.js';
      import {Gltf2Node} from './js/render/nodes/gltf2.js';
      import {SkyboxNode} from './js/render/nodes/skybox.js';
      import {mat4, vec3, quat} from './js/render/math/gl-matrix.js';
      import {QueryArgs} from './js/util/query-args.js';

      // If requested, use the polyfill to provide support for mobile devices
      // and devices which only support WebVR.
      import WebXRPolyfill from './js/third-party/webxr-polyfill/build/webxr-polyfill.module.js';
      if (QueryArgs.getBool('usePolyfill', true)) {
        let polyfill = new WebXRPolyfill();
      }

      // Inline sessions, by default, us a vertical field of view of 90 degrees
      // when computing projection matrices. If an application wants to use a
      // different FoV for inline sessions it can be specified by setting the
      // inlineVerticalFieldOfView value in an updateRenderState call. Note that
      // this only applies to inline sessions, and attempting to set that value
      // for an immersive session will throw an error.
      let inlineSession = null;
      let fov = document.getElementById('vertFOV');
      let fovLabel = document.getElementById('vertFOVLabel');
      function updateFov() {
        let value = parseFloat(fov.value);
        // The inlineVerticalFieldOfView is specified in radians.
        let radValue = value * (Math.PI / 180);

        if (inlineSession) {
          // As with any values set with updateRenderState, this will take
          // effect on the next frame.
          inlineSession.updateRenderState({
            inlineVerticalFieldOfView: radValue
          });
        }
        
        // Set the label on the page
        let label = `Vertical FOV: ${value} degrees`;
        if (value == 90) {
          label += ' (default)';
        }
        fovLabel.textContent = label;
      }
      fov.addEventListener('change', updateFov);

      // XR globals.
      let xrButton = null;
      let xrImmersiveRefSpace = null;
      let xrInlineRefSpace = null;

      // WebGL scene globals.
      let gl = null;
      let renderer = null;
      let scene = new Scene();
      let solarSystem = new Gltf2Node({url: 'media/gltf/space/space.gltf'});
      scene.addNode(solarSystem);
      scene.addNode(new SkyboxNode({url: 'media/textures/milky-way-4k.png'}));

      function initXR() {
        xrButton = new WebXRButton({
          onRequestSession: onRequestSession,
          onEndSession: onEndSession
        });
        document.querySelector('header').appendChild(xrButton.domElement);

        if (navigator.xr) {
          navigator.xr.isSessionSupported('immersive-vr').then((supported) => {
            xrButton.enabled = supported;
          });

          // Start up an inline session, which should always be supported on
          // browsers that support WebXR regardless of the available hardware.
          navigator.xr.requestSession('inline').then((session) => {
            inlineSession = session;
            onSessionStarted(session);
            updateFov();
          });
        }
      }

      function onRequestSession() {
        return navigator.xr.requestSession('immersive-vr').then((session) => {
          xrButton.setSession(session);
          // Set a flag on the session so we can differentiate it from the
          // inline session.
          session.isImmersive = true;
          onSessionStarted(session);
        });
      }

      function onSessionStarted(session) {
        session.addEventListener('end', onSessionEnded);

        if (!gl) {
          gl = createWebGLContext({
            xrCompatible: true
          });

          // In order for an inline session to be used we must attach the WebGL
          // canvas to the document, which will serve as the output surface for
          // the results of the inline session's rendering.
          document.body.appendChild(gl.canvas);
          
          // The canvas is synced with the window size via CSS, but we still
          // need to update the width and height attributes in order to keep
          // the default framebuffer resolution in-sync.
          function onResize() {
            gl.canvas.width = gl.canvas.clientWidth * window.devicePixelRatio;
            gl.canvas.height = gl.canvas.clientHeight * window.devicePixelRatio;
          }
          window.addEventListener('resize', onResize);
          onResize();

          // Installs the listeners necessary to allow users to look around with
          // inline sessions using the mouse or touch.
          addInlineViewListeners(gl.canvas);

          renderer = new Renderer(gl);

          scene.setRenderer(renderer);
        }
        
        // WebGL layers for inline sessions won't allocate their own framebuffer,
        // which causes gl commands to naturally execute against the default
        // framebuffer while still using the canvas dimensions to compute
        // viewports and projection matrices.
        let glLayer = new XRWebGLLayer(session, gl);

        session.updateRenderState({
          baseLayer: glLayer
        });

        let refSpaceType = session.isImmersive ? 'local' : 'viewer';
        session.requestReferenceSpace(refSpaceType).then((refSpace) => {
          // Since we're dealing with multiple sessions now we need to track
          // which XRReferenceSpace is associated with which XRSession.
          if (session.isImmersive) {
            xrImmersiveRefSpace = refSpace;
          } else {
            xrInlineRefSpace = refSpace;
          }
          session.requestAnimationFrame(onXRFrame);
        });
      }

      function onEndSession(session) {
        session.end();
      }

      function onSessionEnded(event) {
        // Only reset the button when the immersive session ends.
        if (event.session.isImmersive) {
          xrButton.setSession(null);
        }
      }

      // Called every time a XRSession requests that a new frame be drawn.
      function onXRFrame(t, frame) {
        let session = frame.session;
        // Ensure that we're using the right frame of reference for the session.
        let refSpace = session.isImmersive ?
                         xrImmersiveRefSpace :
                         xrInlineRefSpace;

        // Account for the click-and-drag mouse movement or touch movement when
        // calculating the viewer pose for inline sessions.
        if (!session.isImmersive) {
          refSpace = getAdjustedRefSpace(refSpace);
        }

        let pose = frame.getViewerPose(refSpace);

        scene.startFrame();

        session.requestAnimationFrame(onXRFrame);

        if (pose) {
          let glLayer = session.renderState.baseLayer;
          gl.bindFramebuffer(gl.FRAMEBUFFER, glLayer.framebuffer);
          gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

          for (let view of pose.views) {
            let viewport = glLayer.getViewport(view);
            gl.viewport(viewport.x, viewport.y,
                        viewport.width, viewport.height);

            scene.draw(view.projectionMatrix, view.transform);
          }
        }

        scene.endFrame();
      }

      // Inline view adjustment code
      // Allow the user to click and drag the mouse (or touch and drag the
      // screen on handheld devices) to adjust the viewer pose for inline
      // sessions. Samples after this one will hide this logic with a utility
      // class (InlineViewerHelper).
      let lookYaw = 0;
      let lookPitch = 0;
      const LOOK_SPEED = 0.0025;

      // XRReferenceSpace offset is immutable, so return a new reference space
      // that has an updated orientation.
      function getAdjustedRefSpace(refSpace) {
        // Represent the rotational component of the reference space as a
        // quaternion.
        let invOrientation = quat.create();
        quat.rotateX(invOrientation, invOrientation, -lookPitch);
        quat.rotateY(invOrientation, invOrientation, -lookYaw);
        let xform = new XRRigidTransform(
            {x: 0, y: 0, z: 0},
            {x: invOrientation[0], y: invOrientation[1], z: invOrientation[2], w: invOrientation[3]});
        return refSpace.getOffsetReferenceSpace(xform);
      }

      function rotateView(dx, dy) {
        lookYaw += dx * LOOK_SPEED;
        lookPitch += dy * LOOK_SPEED;
        if (lookPitch < -Math.PI*0.5)
            lookPitch = -Math.PI*0.5;
        if (lookPitch > Math.PI*0.5)
            lookPitch = Math.PI*0.5;
      }

      // Make the canvas listen for mouse and touch events so that we can
      // adjust the viewer pose accordingly in inline sessions.
      function addInlineViewListeners(canvas) {
        canvas.addEventListener('mousemove', (event) => {
          // Only rotate when the right button is pressed
          if (event.buttons && 2) {
            rotateView(event.movementX, event.movementY);
          }
        });

        // Keep track of touch-related state so that users can touch and drag on
        // the canvas to adjust the viewer pose in an inline session.
        let primaryTouch = undefined;
        let prevTouchX = undefined;
        let prevTouchY = undefined;

        // Keep track of all active touches, but only use the first touch to
        // adjust the viewer pose.
        canvas.addEventListener("touchstart", (event) => {
          if (primaryTouch == undefined) {
            let touch = event.changedTouches[0];
            primaryTouch = touch.identifier;
            prevTouchX = touch.pageX;
            prevTouchY = touch.pageY;
          }
        });

        // Update the set of active touches now that one or more touches
        // finished. If the primary touch just finished, update the viewer pose
        // based on the final touch movement.
        canvas.addEventListener("touchend", (event) => {
          for (let touch of event.changedTouches) {
            if (primaryTouch == touch.identifier) {
              primaryTouch = undefined;
              rotateView(touch.pageX - prevTouchX, touch.pageY - prevTouchY);
            }
          }
        });

        // Update the set of active touches now that one or more touches was
        // cancelled. Don't update the viewer pose when the primary touch was
        // cancelled.
        canvas.addEventListener("touchcancel", (event) => {
          for (let touch of event.changedTouches) {
            if (primaryTouch == touch.identifier) {
              primaryTouch = undefined;
            }
          }
        });

        // Only use the delta between the most recent and previous events for
        // the primary touch. Ignore the other touches.
        canvas.addEventListener("touchmove", (event) => {
          for (let touch of event.changedTouches) {
            if (primaryTouch == touch.identifier) {
              rotateView(touch.pageX - prevTouchX, touch.pageY - prevTouchY);
              prevTouchX = touch.pageX;
              prevTouchY = touch.pageY;
            }
          }
        });
      }

      // Start the XR application.
      initXR();
    </script>
  </body>
</html>
